Electronically actuated apparatus using solenoid actuator with integrated sensor

ABSTRACT

An electromagnetic actuator having an annular pole piece and an annular armature with surfaces formed thereon through which a magnetic flux passes. The armature is axially movable relative to the pole piece between a first position and a second position. Magnetic flux is efficiently transmitted between the pole piece and the armature and the pole piece can be employed to guide the armature for movement thereon.

This is a divisional application of U.S. Ser. No. 11/507,311 filed Aug.21, 2006, the disclosure of which is hereby incorporated by reference asif fully set forth in detail herein.

INTRODUCTION

The present disclosure generally relates to an annular solenoid withaxially overlapping electromagnet and armature.

It is known in the vehicle axle art to employ an electromagneticactuator to translate members of an assembly into/out of engagement withone another. For example, commonly owned U.S. Pat. No. 6,958,030discloses an electromagnetic locking differential assembly that employsan electromagnetic actuator to selectively couple a side gear to adifferential case to cause the differential assembly to operate in afully locked condition. More specifically, the electromagnetic actuatoris actuated to axially translate an actuating ring (which isnon-rotatably coupled to the differential case) such that dogs on theactuating ring matingly engage dogs that are formed on a face of theside gear opposite the gear teeth. As another example, U.S. PatentApplication Publication No. 2004/0132572 discloses an electromagneticlocking differential assembly that employs an electromagnetic actuatorto selectively operate a ball ramp plate to lock a side gear to adifferential case so that the differential operated in a fully lockedcondition.

SUMMARY

In one form, the present teachings provide an electromagnetic actuatorwith a frame, a coil assembly, an armature and a plunger. The frame isdefined by a U-shaped circumferentially extending channel. The coilassembly is received in the U-shaped circumferentially extending channeland has a coil, which is energizable to generate a magnetic field, and ashell that is formed of a ferrous material. The shell defines a cavityinto which the coil is received. The armature is formed of a ferrousmaterial and is movable relative to the coil assembly along atranslation axis due to a magnetic field produced by the coil when thecoil is energized. The plunger is movable with the armature when thecoil is energized. The plunger is formed of a material having a lowmagnetic susceptibility. The plunger has an annular flange member and arim member that is coupled to an outer periphery of the flange member.The flange member is oriented generally perpendicular to the translationaxis. The rim member is disposed concentrically about the translationaxis and is engaged to a radial outer surface of the shell.

In another form, the present teachings provide an electromagneticactuator with a coil assembly and an armature. The coil assembly has acoil, which is energizable to generate a magnetic field, and a shellthat is formed of a ferrous material. The shell defines a cavity intowhich the coil is received. The shell has a circumferentially extendingprojection that encircles an axially extending portion of the coil. Theshell also has a first cylindrical guide surface. The armature is formedof a ferrous material and is movable relative to the coil assembly alonga translation axis due to a magnetic field produced by the coil when thecoil is energized. The armature has a second cylindrical guide surfacethat is slidably engaged upon the first cylindrical guide surface.Magnetic field lines associated with the magnetic field generated by thecoil extend through an interface between the first and secondcylindrical guide surfaces. The magnetic field lines also extend throughan interface between a circumferentially extending surface on thearmature and a circumferentially extending surface on thecircumferentially extending projection.

Further areas of applicability will become apparent from the descriptionprovided herein. It should be understood that the description andspecific examples are intended for purposes of illustration only and arenot intended to limit the scope of the present disclosure.

BRIEF DESCRIPTION OF THE DRAWINGS

The drawings described herein are for illustration purposes only and arenot intended to limit the scope of the present disclosure in any way.

FIG. 1 is a front view of an actuator assembly constructed in accordancewith the teachings of the present disclosure;

FIG. 2 is a side elevation of the actuator assembly of FIG. 1;

FIG. 3 is a sectional view taken along the line 3-3 of FIG. 1;

FIG. 4 is a front view of a portion of the actuator assembly of FIG. 1illustrating the frame in more detail;

FIG. 5 is a section view taken along the line 5-5 of FIG. 4;

FIG. 6 is a partial side elevation view of the frame;

FIG. 7 is a front view of a portion of the actuator assembly of FIG. 1illustrating the outer shell in more detail;

FIG. 8 is a sectional view taken along the line 8-8 of FIG. 7;

FIG. 9 is a perspective view of a portion of the actuator assembly ofFIG. 1 illustrating the inner shell in more detail;

FIG. 10 is a longitudinal section view of the inner shell;

FIG. 11 is a front view of a portion of the actuator assembly of FIG. 1illustrating the coil in more detail;

FIG. 12 is a sectional view taken along the line 12-12 of FIG. 11;

FIG. 13 is a longitudinal sectional view of a portion of the actuatorassembly of FIG. 1 illustrating the armature in more detail;

FIG. 14 is an enlarged portion of FIG. 13;

FIG. 15 is a perspective view of a portion of the actuator assembly ofFIG. 1 illustrating the plunger in more detail;

FIG. 16 is a sectional view taken along the line 16-16 of FIG. 1;

FIG. 17 is a schematic sectional view of a portion of the sensorassembly;

FIG. 18 is a plot illustrating the output of the sensor signal producedby the sensor assembly as a function of the relative position of thesensor target;

FIG. 19 is a schematic illustration of the coil assembly and sensorassembly as coupled to a power source and a controller;

FIG. 20 is an elevation view illustrating the calibration of the sensorassembly after the actuator assembly of FIG. 1 has been assembled;

FIG. 20A is a front view of another actuator assembly constructed inaccordance with the teachings of the present disclosure, the actuatorincluding a sensor assembly having redundant sensor portions;

FIG. 21 is a schematic illustration of a vehicle having a drivelineconstructed in accordance with the teachings of the present disclosure;

FIG. 22 is a partially broken away perspective view of a portion of thevehicle of FIG. 21, illustrating the rear axle assembly in more detail;

FIG. 23 is an exploded perspective view of a portion of the rear axleassembly, illustrating the differential assembly in more detail;

FIG. 24 is a partially broken away perspective view of the differentialassembly;

FIG. 25 is an exploded perspective view of a portion of the rear axleassembly, illustrating the differential assembly in more detail;

FIG. 26 is a front view of another actuator assembly constructed inaccordance with the teachings of the present disclosure;

FIG. 27 is a sectional view taken along the line 27-27 of FIG. 26;

FIG. 28 is a side elevation of the actuator assembly of FIG. 26;

FIG. 29 is a partial perspective view of a portion of an alternativelyconstructed plunger; and

FIGS. 30 through 32 are partial schematic views illustrating the plungerof FIG. 29 as incorporated into other actuator assemblies constructed inaccordance with the teachings of the present disclosure.

DETAILED DESCRIPTION OF THE VARIOUS EMBODIMENTS

With reference to FIGS. 1 through 3 of the drawings, an actuatorassembly constructed in accordance with the teachings of the presentinvention is generally indicated by reference numeral 10. The actuatorassembly 10 can include a frame 20, a coil assembly 22, an armature 24,a plunger 26 and a sensor assembly 28.

With reference to FIGS. 4 through 6, the frame 20 can be formed of asuitable material, such as a material having a low magneticsusceptibility (e.g., 316 stainless steel), and can include an outer orfirst annular sidewall 34, an inner or second annular sidewall 36, anendwall 38 and a sensor mount 40. The endwall 38 can be coupled to thefirst and second annular sidewalls 34 and 36 so as to define an interiorannular recess 42 that is bounded on three sides by the first and secondsidewalls 34 and 36 and the endwall 38. The second annular sidewall 36can define a through-hole 44 and may optionally include a lip portion 46that extends radially inwardly to somewhat close one side of the throughhole 44. The configuration of the sensor mount 40 is tailored to theconfiguration of the particular sensor assembly 28 employed. In theparticular example provided, the sensor mount 40 includes a mountingnotch 50, which is formed in the endwall 38 and the first annularsidewall 34, and a mounting aperture 52 that is formed in the endwall38.

Returning to FIG. 3, the coil assembly 22 can include an outer shell 60,an inner shell 62 and a coil 64. When positioned in the recess 42 of theframe 20, the outer and inner shells 60 and 62 can cooperate to form acore structure 66 that defines an annular coil aperture 68 that is sizedto receive the coil 64. The coil assembly 22 can cooperate with theframe 20 to define an armature space 70 in an area that is locatedradially outward of the coil assembly 22 and inwardly of the firstannular sidewall 34.

With additional reference to FIGS. 7 and 8, the outer shell 60 can beformed of a suitable material, such as SAE 1008 steel, and can includean annular body 80 and an annular lip member 82 that can extend radiallyoutwardly from the outer edge of the annular body 80. The annular body80 can be sized to be received in the annular recess 42 in the frame 20and can include a coil mount 84 having a pair of threaded apertures 86and a coupling window 88. The annular lip member 82 can include achamfered interior edge surface 90. In the example provided, the angleof the chamfer is about 25°.

With reference to FIGS. 3, 9 and 10, the inner shell 62 can be formed ofa suitable material, such as SAE 1008 steel, and can include a tubularbody 90 and a radially projecting wall 92. The tubular body 90 can besized to be received within the annular recess 42 and abut the secondannular sidewall 36. The radially projecting wall 92 can extend radiallyfrom an end of the tubular body 90 so as to abut the first annularsidewall 34. The radially projecting wall 92 can include a first flangeportion 94, a second flange portion 96 and a circumferentially extendingprojection 98 that can be formed between the first and second flangeportions 94 and 96 proximate a distal end of the radially projectingwall 92. The circumferentially extending projection 98 can be generallyV-shaped, having a first tapered face portion 100, which can intersectthe first flange portion 94, and a second tapered face portion 102 thatcan intersect the second flange portion 96. In the particular exampleprovided, the first tapered face portion 100 is disposed at an angle ofabout 128° from the first flange portion 94 and the second tapered faceportion 102 is disposed at an angle of about 74° from the second flangeportion 96.

In FIGS. 3, 11 and 12, the coil 64 can include a coil winding 110, apair of terminals 112 and a coil overmold member 114. The coil winding110 can be formed of an appropriate material, such as 168 turns ofPOLYBONDEX® (polyester/polyaimdeimide/bondcoat) 21 AWG copper wirehaving a nominal resistance of about 2.9 ohms. It will be appreciatedthat the turns of the coil winding 110 can be wound about thelongitudinal axis of the coil winding 110 in a conventional and wellknown manner. The terminals 112 can be formed of a suitable conductor,such as 18 AWG Teflon® coated copper wire and can be employed toelectrically couple the coil winding 110 to a source of electricalenergy (not shown). The terminals 112 of the coil 64 can be fittedthrough the coupling window 88 (FIG. 7) in the outer shell 60. The coilwinding 110 can be fully or partially encapsulated in the coil overmoldmember 114 to thereby provide the coil winding 110 with structuralintegrity that permits the coil 64 to be assembled to the remainder ofthe actuator assembly 10. The coil overmold member 114 can be formed ofan appropriate and well known electrically insulating thermoplasticmaterial, such as ZYTEL® HTN 54615 HSLR marketed by E.I. du Pont deNemours and Company or EpoxySet EC-1012M Epoxicast with an EH-20Mhardener mixed at a rate of 100:10.

With reference to FIGS. 3, 13 and 14, the armature 24 can be formed of asuitable material, such as a low carbon steel (e.g., SAE 1008 steel),and can include an annular body 120 and a sensor portion 122. Theannular body 120 can include a first end 124, a second end 126, aninterior surface 128 and a tapered surface 130 that intersects theinterior surface 128 and the second end 126. In the example provided,the first and second ends 124 and 126 are generally perpendicular to thelongitudinal axis 132 of the armature 24 and the angle between thetapered surface 130 and the longitudinal axis 132 of the armature isabout 16°.

The sensor portion 122 can extend radially outwardly from the annularbody 120 and can be disposed about the circumference of the annular body120. The sensor portion 122 can have first and second surfaces 134 and136, respectively, that can be oriented generally perpendicular to thelongitudinal axis 132 of the armature 24. It will be appreciated thatthe sensor portion 122 need not be formed in a circumferentiallyextending manner. For example, the sensor portion 122 could be formed asa single tooth that extends radially from the annular body 120 over onlya portion of the circumference of the annular body 120. Configuration inthis manner would require corresponding changes to the frame 20, thetubular body 120 and/or the plunger 26 to facilitate the “keying” of thearmature 24 to the frame 20 and the armature's 24 movement of theplunger 26.

The armature 24 can be disposed in the armature space 70 and can axiallytranslate within the recess 42 in the frame 20. It will be appreciatedthat the tapered surface 130 of the armature 24 cooperates with thesecond tapered face portion 102 (FIG. 10) of the inner shell 62 topermit the armature 24 to axially overlap the inner shell 62 withoutcontacting the core structure 66 along this tapered interface. It willalso be appreciated that the second end 126 of the armature 24 willcontact the second flange portion 96 (FIG. 10) of the inner shell 62before the tapered surface 130 and the second tapered face portion 102(FIG. 10) contact one another so that an air gap will always existbetween the tapered surface 130 and the second tapered face portion 102(FIG. 10).

In FIGS. 3 and 15, the plunger 26 can be formed of an appropriatematerial, such as a material having a low magnetic susceptibility (e.g.,316 stainless steel), and can be a cap-like structure having a flangemember 140 and a side wall or rim member 142. The flange member 140 canbe a ring-shaped plate and can include a plurality of circumferentiallyspaced-apart apertures 144. The rim member 142 can be coupled to theouter radial edge of the flange member 140 and can extend about thecircumference of the flange member 140. A plurality of circumferentiallyspaced-apart apertures 146 can be formed through the rim member 142. Theapertures 144 and 146 can be configured to permit the plunger 26 to moreeasily translate. For example, the apertures 144 and 146 can reduce themass of the plunger 26 and as such, it will be appreciated that theirquantities, shape and size may be selected based on the parameters of agiven application. Such design choices are within the ordinary level ofskill in the art and as such, need not be explained in detail herein.The circumference of the rim member 142 can be sized so that the rimmember 142 can be received in the recess 42 radially outwardly of thecore structure 66 and the flange member 140 can be abutted against thecore structure 66 on a side opposite the endwall 38 of the frame 20. Adistal end 148 of the rim member 142 can abut a portion of the armature24, such as the first surface 134 (FIG. 14) of the sensor target 122.

Returning to FIGS. 1 and 2 and with additional reference to FIGS. 16 and17, the sensor assembly 28 can include a back-biased Hall-effect sensor,such as an AT635LSETN-T sensor marketed by Allegro MicroSystems ofWorcester Mass. The sensor assembly 28 can include a housing 200 and asensor portion 202. The housing 200 can be a thermoplastic material thatcan be overmolded onto the sensor portion 202 and can define a locator208 (FIG. 2) that can be sized and shaped to matingly engage edges ofthe mounting aperture 52 (FIG. 4) formed in the endwall 38 and the firstannular sidewall 34 of the frame 20. As will be appreciated, thelocator(s) on the housing 200 can cooperate with the mounting aperture52 and other features of the frame 20 to position the sensor assembly 28in a predetermined location relative to the sensor target 122 (FIG. 3).The sensor assembly 28 can be coupled to the frame 20 in any appropriatemanner, such as epoxy bonding or overmolding. Such techniques are wellknown in the art and as such, need not be discussed in detail herein. Inthe particular example provided, an overmold 210 is applied to thesensor portion 202 to fixedly couple the sensor portion 202 to the frame20.

With reference to FIG. 17, the sensor portion 202 can include a circuit220 and a magnet 222. As will be appreciated, the magnet 222 is operablefor producing a magnetic field and the circuit 220 can include aHall-effect circuit that can be operable for sensing the magnetic field.Positioning of the sensor target 122 (FIG. 3) within the magnetic fieldcan alter the field lines of the magnetic field and these alterationscan be sensed by the circuit 220. Accordingly, the circuit 220 canproduce a sensor signal that is responsive to a position of the sensortarget 122 (FIG. 3). In the example provided, the circuit 220 can switchon and off in response to the position of the sensor target 122 (FIG. 3)relative to the sensor portion 202. The circuit 220 can be a digital,programmable, true-power-on Hall-effect circuit. In this regard, thecircuit 220 can provide a first digital switch output (e.g., a low logiclevel) when the sensor target 122 (FIG. 3) is in a first position andthe circuit 220 is in a first state (e.g., corresponding to a high logiclevel) and a second digital switch output (e.g., a high logic level)when the sensor target 122 (FIG. 3) is in a second position and thecircuit 220 is in a second state (e.g., corresponding to low logiclevel).

The output of the circuit 220 is schematically illustrated in FIG. 18.With additional reference to FIGS. 3 and 17, movement of the sensortarget 122 in the direction X when the state condition of the circuit220 is low does not effect the state condition of the circuit 220 whenthe sensor target is in-line with the second position 230 andconsequently, the circuit 220 continues to output the first digitalswitch output. Continued movement of the sensor target in the directionX positions the sensor target at the first position 232, which causesthe circuit 220 to switch to from a low logic state 226 to a high logicstate 228 and the circuit 220 responsively produces the second digitalswitch output. Thereafter, the sensor target can move further in thedirection X or can move toward the second position 230 (but not in-linewith the second position 230) without affecting the output of thecircuit 220.

When the circuit 220 is in the high logic state and the sensor target ismoved in-line with the second position 230, the circuit 220 will switchfrom the high logic state 228 to the low logic state 226 and the circuit220 responsively produces the first digital switch output. Thereafter,the sensor target 122 can move further in a direction opposite thedirection X or can move toward the first position 232 (but not in-linewith the first position 232) without affecting the output of the circuit220.

With reference to FIG. 19, it will be appreciated that the terminals 112of the coil 64 can be selectively coupled to a source of electricalpower, such as a battery 250. The circuit 220 can include an inputterminal 252, which is configured to receive an electrical input of apredetermined voltage, and an output terminal 254 that is configured totransmit the first and second digital switch outputs to a controller256. A capacitor 258 can be electrically coupled to the input terminal252 and the output terminal 254 to attenuate electrical noise.

With additional reference to FIG. 3, electrical power can be applied tothe coil 64 to actuate the actuator assembly 10, wherein a magneticfield produced by the coil 64 will drive the armature 24 in an actuatingdirection (i.e., a direction opposite the endwall 38 of the frame 20).As the distal end 148 of the rim member 142 of the plunger 26 is abuttedagainst the first surface 134 of the sensor target 122, translation ofthe armature 24 in the actuating direction will cause correspondingtranslation of the plunger 26.

As the circuit 220 of the sensor assembly 28 is programmable in theexample provided, the actuator assembly 10 can be positioned in asetting jig or fixture 280 as shown in FIG. 20 between a datum surface282 and a gauging surface 284 that is spaced apart from the datumsurface 282 by a predetermined distance. The actuator assembly 10 can beactuated so that the plunger 26 is extended sufficiently such that anon-moving portion of the actuator assembly 10 (e.g., the frame 20) isabutted against one of the datum surface 282 and the gauging surface 284while the plunger 26 is abutted against the other one of the datumsurface 282 and the gauging surface 284. It will be appreciated that thesensor target 122 will be positioned in a predetermined position (e.g.,the first position) and as such, the circuit 220 may be programmed toidentify this condition. In the example provided, the circuit 220 isconfigured such that the setting of one position (e.g., the firstposition) will automatically set or establish the other position (e.g.,the second position).

In view of the above, it will be appreciated that the actuator assembly10 may be pre-programmed and thereafter assembled to a drivelinecomponent, such as a locking differential or a transfer case, withoutfurther programming or calibration in certain applications. Thepre-programming of the sensor assembly 28 is particularly advantageousin that it permits the programming to be performed prior to theinstallation of the actuator assembly 10 to the driveline component inan environment where the programming may be performed in a relativelymore efficient manner with relatively simple and inexpensive tooling(i.e., tooling that is not based on the configuration of the drivelinecomponent). Moreover, pre-programming of the actuator assembly 10eliminates the need for further programming and/or calibration shouldthe actuator assembly 10 be replaced when the driveline component isserviced.

While the sensor assembly 28 and the sensor portion 202 have beenillustrated and described herein as including a back-biased Hall-effectsensor, those of ordinary skill in the art will appreciate that anyappropriate type of sensor may be employed in the alternative. Forexample, the sensor assembly 28 and the sensor portion 202 could includea magnetoresistive sensor or a magnetostrictive sensor, such as amagnetoresistive or magnetostrictive Hall-effect sensor, as such sensorscan be somewhat less influenced by a change in the magnitude of themagnetic field proximate the sensor assembly 28. It will also beappreciated that the sensor assembly 28 can include a second sensorportion 202′ as shown in FIG. 20A. The dual sensor portions 202, 202′provide a level of redundancy that may be desirable in some situations.

With reference to FIG. 21, a motor vehicle 300 is illustrated to includea drive train 302 that incorporates an actuator assembly constructed inaccordance with the teachings of the present disclosure. The motorvehicle 302 can include a power source 304, such as an internalcombustion engine, and a transmission 306 that can provide rotary powerto the drive train 302 in a manner that is well known in the art. In theexample provided, the drive train 302 includes a transfer case 312, afirst or front axle assembly 314, a second or rear axle assembly 316, afirst propeller shaft 318, which conventionally couples the front axleassembly 314 to a front output shaft 320 of the transfer case 312, and asecond propeller shaft 322 that conventionally couples the rear axleassembly 316 to a rear output shaft 324 of the transfer case 312. Thetransfer case 312 can receive rotary power from the transmission 306 andcan distribute rotary power to the front and rear axle assemblies 314and 316 in a desired manner.

The front and rear axle assemblies 314 and 316 can be similar in theirconstruction and operation and as such, only the rear axle assembly 316will be discussed in detail herein. With additional reference to FIG.22, the rear axle assembly 316 can include an axle housing 350, adifferential assembly 352 and a pair of axle shafts 354 (only one ofwhich is specifically shown). The axle housing 350 can be conventionallyconfigured and can include a housing structure 360 and a pair of bearingcaps 362 that can be fixedly but removably coupled to the housingstructure 360. The housing structure 360 can define a differentialcavity 364 that houses the differential assembly 352. The bearing caps362 can be decoupled from the housing structure 360 to permit thedifferential assembly 352 to be received within the differential cavity364. The axle shafts 354 can be coupled to opposite sides of thedifferential assembly 352 and to respective ones of the rear vehiclewheels 362 (FIG. 21) in any appropriate manner.

With additional reference to FIGS. 23 and 24, the differential assembly352 can include a differential case 400, a ring gear 402 (FIG. 22), agear set 404, a locking system 406 and an input pinion 408 (FIG. 22).The input pinion 408 and the ring gear 402 can be conventionallyconstructed and mounted in the axle housing 350 and as such, need not bediscussed in significant detail herein. Briefly, the input pinion 408can be coupled to the axle housing 350 via a set of bearings (notspecifically shown) and disposed about a rotational axis that isgenerally perpendicular to a rotational axis of the differential case400. The input pinion 408 can include a plurality of pinion teeth (notshown) that can be meshingly engaged to a plurality of ring gear teeth(not specifically shown) formed on the ring gear 402.

The differential case 400 can include a body portion 420 and acircumferentially-extending flange 422 that is coupled to (e.g.,integrally formed with) the body portion 420. The flange 422 can includea plurality of apertures 424 that can facilitate the removable couplingof the ring gear 402 via a plurality of threaded fasteners 426.

The body portion 420 can define a gear set cavity 430 and one or moreassembly windows 432, which can be employed to install the gear set 404into the gear set cavity 430. In the example provided, the body portion420 includes first and second side segments 440 and 442, respectively,and first and second end segments 444 and 446, respectively. Each of thefirst and second side segments 440 and 442 can include a through-bore448, which can be arranged generally perpendicular to the rotationalaxis of the differential case 400, and a boss 450 that can be disposedconcentrically about the through-bore 448 within the gear set cavity430. A relatively large fillet radius 452 can be employed at theintersection between the second end segments and the first and secondside segments 440 and 442.

Each of the first and second end segments 444 and 446 can span betweenthe first and second side segments 440 and 442 and can include a hollow,axially extending trunnion 450. Each trunnion 450 can define an insidediameter, which can be sized to receive a corresponding one of the axleshafts 354 there through, and an outside diameter that can be sized toengage a bearing 454 (FIG. 22) that is disposed between the housingstructure 360 and the bearing cap 362. Those of ordinary skill in theart will appreciate that the differential case 400 may be may be mountedto the axle housing 350 via the bearings 454 for rotation within thedifferential cavity 364 about the aforementioned rotational axis.

A retaining bore 458 can be formed through the first end segment 444 anda portion of the second side segment 442 and can intersect thethrough-bore 448. A first annular pocket 460 can be formed in theinterior face of the first end segment 444 and can be concentric withthe trunnion 450. The first annular pocket 460 can include a first boreportion 462 and a second bore portion 464 that can be concentric withand relatively smaller in diameter than the first bore portion 462.

The second end segment 446 can include an outer portion that defines amounting hub 470 and an interior portion that defines a second annularpocket 472. The mounting hub 470 can be disposed between the flange 422and the trunnion 450 and can include an actuator mount surface 480 thatcan be generally concentric with the trunnion 450. A circumferentiallyextending groove 482 can be formed in the actuator mount surface 480. Aplurality of actuator apertures 484 can be formed axially through thesecond end segment 446 and can intersect the second annular pocket 472.The second annular pocket 472 can include a pocket portion 490, aplurality of locking features 492 and a thrust ring pocket 494. In theexample provided, the pocket portion 490 is generally circular in shapeand the locking features 492 can be recesses that can intersect thepocket portion 490. The locking features 492 can be shaped in anyappropriate manner and in the example provided, have a half-circle shapethat extends from the pocket portion 490. The thrust ring pocket 494 canbe circular in shape and concentric with the pocket portion 490.

The gear set 404 can include first and second side gears 500 and 502,respectively, first and second pinion gears 504 and 506, respectively, across-shaft 508 and a retaining bolt 510. The first side gear 500 caninclude an annular gear portion 520, which can have a plurality of gearteeth, an annular hub portion 522, which can intersect the gear portion520 at a flange face 524, and a splined aperture 526 that can engage amating splined segment (not shown) formed on a corresponding one of theaxle shafts 354. The hub portion 522 can be sized to be received in thesecond bore portion 464 in the first end segment 444, while a portion ofthe gear portion 520 can be received in the first bore portion 462. Inthe particular example provided, a thrust washer 530 is disposed overthe hub portion 522 and abuts the flange face 524.

The second side gear 502 can include a gear portion 540, which can havea plurality of gear teeth, a tubular hub portion 542 and a splinedaperture 546. The tubular hub portion 542 can axially extend from thesecond side gear 502 in a direction opposite the gear portion 540. Thesplined aperture 546 can be formed through the tubular hub portion 542and can engage a mating splined segment (not shown) formed on acorresponding one of the axle shafts 354. The second side gear 502 canbe received in the first pocket portion 490 of the second end segment446. A thrust washer 560 can be disposed in the thrust ring pocket 494between the interior surface 562 of the second end segment 446 and anaxial end face 564 of the tubular hub portion 542. It will beappreciated that the thickness of the thrust washer 560 can be selectedto control the lash between the teeth of the second side gear 502 andthe teeth of the first and second pinion gears 504 and 506.

The first and second pinion gears 504 and 506 can be rotatably mountedon the cross-shaft 508 and meshingly engaged to the teeth of the firstand second side gears 500 and 502. The cross-shaft 508 can extendthrough the through-bores 448 in the first and second side segments 440and 442. Washer-like spacers 470 can be employed to control the lashbetween the first and second pinion gears 504 and 506 and the first andsecond side gears 500 and 502. The retaining bolt 510 can be insertedinto the retaining bore 458 and threadably engaged to a mating threadedaperture 472 formed in the cross-shaft 508 to thereby fixedly securecross-shaft 508 to the differential case 400.

The locking system 406 can include a first dog ring 600, a second dogring 602, a return spring 604, a spacer ring 606, a thrust plate 608, anactuator assembly 10 a and a retaining ring 610.

With reference to FIGS. 23 through 25, the first dog ring 600 can becoupled (e.g., integrally formed) with the second side gear 502 on aportion thereof opposite the gear portion 540. The first dog ring 600can include a plurality of circumferentially spaced apart radiallyextending teeth 620 and a circular groove 622 that can be disposedbetween the tubular hub portion 542 and the teeth 620. In the exampleprovided, the teeth 620 are relatively numerous and shallow so as toprovide increased strength and load sharing between the teeth 620 aswell as to lower tooth contact stresses.

The second dog ring 602 can include an annular body portion 640, aplurality of mating locking features 642, a circular groove 644 and apilot portion 646. The annular body portion 640 can be received in thepocket portion 490 of the second annular pocket 472 and can include aplurality of teeth 650 that are configured to matingly engage the teeth620 of the first dog ring 600. The circular groove 644 can be disposedradially inwardly of the teeth 650 and can generally correspond to thecircular groove 482 formed in the first dog ring 600. The pilot portion646 can be an annular axially projecting rim that can aid in retainingthe return spring 604 to the second dog ring 602. Additionally oralternatively, the pilot portion 646 can engage a mating feature formedon the first dog ring 600 or the second side gear 502 that can guide oraid in guiding the teeth 650 of the second dog ring 602 into engagementwith the teeth 620 of the first dog ring 600. The mating lockingfeatures 642 can be coupled to the annular body portion 640 and in theexample provided, comprise tabs that are semi-circular in shape. Themating locking features 642 are configured to engage the lockingfeatures 492 in the second annular pocket 472 to permit the second dogring 602 to be non-rotatably coupled to the differential case 400 butaxially movable relative to the differential case 400 along therotational axis of the differential case 400.

The spacer ring 606 can be disposed within the pocket portion 490 aboutthe locking features 492 and can be positioned axially between thesecond dog ring 602 and the surface 490 a of the pocket portion 490. Thereturn spring 604 can be any appropriate spring and can bias the firstand second dog rings 600 and 602 apart from one another. In the exampleprovided, the return spring 604 is a double wave spring that can bedisposed in the circular grooves 622 and 644. It will be appreciatedthat the return spring 604 can bias the second dog ring 602 intoabutment with the spacer ring 606 and the spacer ring 606 into abutmentwith the second end segment 446.

The thrust plate 608 can include a plate portion 700 and a plurality ofleg members 702. The plate portion 700 can have an annular shape and canbe sized so as to be slidably received over the actuator mount surface480. The leg members 702 can be coupled to the plate portion 700 and canextend axially through the actuator apertures 484 formed in the secondend segment 446. The end of the leg members 702 opposite the plateportion 700 can engage the second dog ring 602 in an appropriate area.In the example provided, the thrust plate 608 include four leg members702 each of which abutting a corresponding one of the mating lockingfeatures 642.

The actuator assembly 10 a can be generally similar to the actuatorassembly 10 described above in conjunction with FIGS. 1 through 19,except that the actuator assembly 10 a includes a bushing 750 and ananti-rotate bracket 752. With reference to FIGS. 26 and 27, the bushing750 can be formed of an appropriate material, such as an oil-impregnatedsintered bronze conforming to ASTM B438. The bushing 750 can have anouter diameter, which can be sized to engage the second annular sidewall36 via an interference fit. The bushing 750 can be pressed into theannular recess 42 such that an end of the bushing 750 abuts the annularlip 46. The bushing 750 can define an inner diameter that is sized to bejournally supported on the actuator mount surface 480 (FIG. 24) of themounting hub 470 (FIG. 24) of the differential case 400 (FIG. 24).

The anti-rotate bracket 752 can be formed of an appropriate material,such as a material having a low magnetic susceptibility (e.g., 316stainless steel), and can include one or more tab members 760 that canbe coupled to the frame 20. In the particular example provided, theanti-rotate bracket 752 is a discrete structure that includes an annularbody portion 762 that can be coupled to the frame member 20 by anappropriate coupling means, such as fasteners (e.g., threaded fasteners,rivets), welds or adhesives. The tab members 760 can extend generallyperpendicular to the annular body portion 762 and are configured toengage the opposite lateral surfaces of an associated one of the bearingcaps 362 (FIG. 22) so as to inhibit relative rotation between the axlehousing 350 (FIG. 22) and the actuator assembly 10 a. It will beappreciated, however, that the tab members 760 could be integrallyformed with the frame 20 in the alternative.

Returning to FIGS. 23 and 24, the actuator assembly 10 a can be slidablyreceived onto the mounting hub 470 such that the plunger 26 can beabutted against the plate portion 700 of the thrust plate 608. The snapring 610 can be received in the circumferentially extending groove 482in the actuator mount surface 480 and can inhibit axial withdrawal ofthe actuator assembly 10 a from the mounting hub 470.

When the actuator assembly 10 a is actuated, the plunger 26 willtranslate the thrust plate 608 such that the leg members 702 urge thesecond dog ring 602 toward the first dog ring 600 such that the teeth620 and 650 of the first and second dog rings 600 and 602 engage oneanother. As the second dog ring 602 is non-rotatably coupled to thedifferential case 400 and as the first dog ring 600 is non-rotatablycoupled to the second side gear 502, engagement of the teeth 620 and 650inhibits rotation of the second side gear 502 relative to thedifferential case 400, thereby locking the differential assembly 352 toinhibit speed differentiation between the axle shafts 354 (FIG. 22). Itwill be appreciated that the tab members 760 of the anti-rotate bracket752 can contact the sides of the adjacent bearing cap 362 (FIG. 22) tothereby inhibit or limit rotation of the actuator assembly 10 a relativeto the axle housing 350 (FIG. 22). It will be appreciated that as theactuator 10 a is immersed in a fluid (i.e., a lubricating and coolingoil), the apertures 144 in the plunger 26 can be sized and shaped toreduce surface tension and friction, while the apertures 146 (FIGS. 15and 27) in the plunger 26 can form ports for intaking fluid into andexhausting fluid from the armature space 70 (FIG. 27). Additionally oralternatively, the plunger 26 can be configured such that the flangemember 140 (FIG. 15) can be spaced apart from the coil assembly 22 by apredetermined distance, such as 0.04 inch (1 mm) when the actuator 10 ais in a non-actuated condition and the plunger 26 is fully returnedtoward the coil assembly 22. As those of ordinary skill in the art willappreciate, it is commonly understood that the volume of a vehiclecomponent should be minimized to improve the packaging of the vehiclecomponent into a particular vehicle. We have found, however, that thespacing between the flange member 140 (FIG. 15) and the coil assembly 22can reduce surface tension and friction, particularly at when thetemperature of the lubricating oil is relatively cold.

It will be appreciated that as the actuator assembly 10 a ispre-programmed/calibrated, the differential assembly 352 may beassembled and tested (as necessary) without calibrating or programmingthe sensor assembly 28 after it has been installed to the differentialcase 400. Moreover, it will be appreciated that as the sensor assembly28 directly senses a position of the armature 24 (FIG. 27) via thesensor portion 122 (FIG. 27), the sensor signal produced by the sensorassembly 28 can be employed to both identify the state in which thedifferential assembly 352 is operated (e.g., locked or unlocked) and theposition of the armature 24 (FIG. 27). This latter information issignificant in that direct sensing of the position of the armature 24(FIG. 27) permits the controller 256 (FIG. 22) to accurately identifythose situations where the armature 24 (FIG. 27) has traveledsufficiently to cause actuation of the differential assembly 352; thecontroller 256 (FIG. 22) may thereafter alter the manner in whichelectrical power is provided to the actuator assembly 10 a. For example,the controller 256 (FIG. 19) may utilize a pulse-width modulatingtechnique to provide electrical power to the actuator assembly 10 a. Thecontroller 256 (FIG. 19) can employ a first, relative high duty cycle sothat the apparent voltage provided to the actuator 10 a is relativelyhigh to initiate movement of the thrust plate 608 to lock thedifferential assembly 352. Thereafter, the controller 256 (FIG. 19) canemploy a second, relatively lower duty cycle in response to a change inthe sensor signal when the sensor target 122 (FIG. 27) is positioned atthe first position. In this regard, a relatively lower duty cycle can beemployed to hold or maintain the actuator 10 a in an actuated condition.The lower duty cycle provides a relatively lower apparent voltage andreduces energy consumption and the generation of heat by the actuator 10a.

While the actuators 10 and 10 a of FIGS. 1 and 27 have been describedthus far as including an armature with an integral sensor target, thoseof ordinary skill in the art will appreciate that the actuator, in itsbroader aspects, may be constructed somewhat differently. For example,the sensor target may be directly coupled to the plunger as shown inFIGS. 29 and 30. In this arrangement, a portion of the side wall or rimmember 142 b of the plunger 26 b can be sheared and bent outwardly toform a sensor tab 1000, while the remainder of the plunger 26 b can beconfigured as described above. A ferro-magnetic target 1002 can beovermolded onto the sensor tab 1000. In the particular example provided,a target aperture 1004 is formed through the sensor tab 1000 and theferro-magnetic material 1002 is overmolded onto the sensor tab 1000 in alocation that corresponds to the target aperture 1004. Theferro-magnetic target 1002 and the sensor tab 1000 cooperate cancooperate to define the sensor target 122 b. A slot 1006 can be formedin the second annular sidewall 36 b of the frame 20 b to receive thesensor tab 1000 and/or the sensor target 122 b when the sensor target122 b translates axially relative to the frame 20 b. The sensor assembly28 b can be coupled to the frame 20 b in a manner that is similar tothat which is described above and can include any appropriate type ofsensor. In the particular example provided, the sensor assembly 28 bincludes a back-biased Hall-effect sensor, such as an AT635LSETN-Tsensor marketed by Allegro MicroSystems of Worcester Mass. Furtherexamples of suitable sensors include magnetoresistive sensors andmagnetostrictive sensors, which could be Hall-effect type sensors.

The example of FIG. 31 is similar to that which is shown in FIGS. 29 and30, except that a forward-biasing magnet 1010 is coupled to the sensortab 1000 rather than the overmolding of a ferro-magnetic material ontothe sensor tab 1000. The forward-biasing magnet 1010 can be fitted intothe target aperture 1004 and secured to the sensor tab 1000 in anydesired manner, such as through adhesives, mechanical couplings and/orovermolding. The sensor assembly 28 c can include a linear hall element1012 can be coupled to the frame 20 b and can cooperate with theforward-biasing magnet 1010 to identify a position of the plunger 26 crelative to the frame 20 b. The example of FIG. 32 is also similar tothat which is shown in FIG. 31, except that the sensor assembly 28 d isa magnetoresistive sensor that is coupled to the frame 20 b. Those ofordinary skill in the art will appreciate that the magnet 1010 can haveany appropriate shape.

It will be appreciated that the arrangements of FIGS. 30 through 32orient the sensor assembly in a manner that is generally perpendicularto an apparent magnetic field of the sensor target. Construction in thismanner can help the sensor assembly to be relatively more tolerant offluctuations in the magnitude of magnetic field of the sensor target.

While specific examples have been described in the specification andillustrated in the drawings, it will be understood by those of ordinaryskill in the art that various changes may be made and equivalents may besubstituted for elements thereof without departing from the scope of thepresent disclosure as defined in the claims. Furthermore, the mixing andmatching of features, elements and/or functions between various examplesis expressly contemplated herein so that one of ordinary skill in theart would appreciate from this disclosure that features, elements and/orfunctions of one example may be incorporated into another example asappropriate, unless described otherwise, above. Moreover, manymodifications may be made to adapt a particular situation or material tothe teachings of the present disclosure without departing from theessential scope thereof. Therefore, it is intended that the presentdisclosure not be limited to the particular examples illustrated by thedrawings and described in the specification as the best mode presentlycontemplated for carrying out this invention, but that the scope of thepresent disclosure will include any embodiments falling within theforegoing description and the appended claims.

1. An electromagnetic actuator comprising: a frame that is defined by aU-shaped circumferentially extending channel; a coil assembly receivedin the U-shaped circumferentially extending channel, the coil assemblyhaving a coil, which is energizable to generate a magnetic field, and ashell that is formed of a ferrous material, the shell defining a cavityinto which the coil is received; an armature that is formed of a ferrousmaterial and which is movable relative to the coil assembly along atranslation axis due to a magnetic field produced by the coil when thecoil is energized; and a plunger that moves with the armature when thecoil is energized, the plunger being formed of a material having a lowmagnetic susceptibility, the plunger having an annular flange member anda rim member that is coupled to an outer periphery of the flange member,the flange member being oriented generally perpendicular to thetranslation axis, the rim member being disposed concentrically about thetranslation axis and being engaged to a radial outer surface of theshell.
 2. The electromagnetic actuator of claim 1, wherein the armatureincludes a tubular body that is received into the rim member.
 3. Theelectromagnetic actuator of claim 2, wherein the rim member terminateson a side opposite the flange member at an axial end face that abuts arib formed on the armature.
 4. The electromagnetic actuator of claim 1,wherein the armature is movable between an extended position, in whichthe flange member of the plunger is axially spaced apart from the coilassembly by a first dimension, and a returned position in which theflange member is axially spaced apart from the coil assembly by asecond, smaller dimension such that the flange member does not contactthe shell when the armature is in the returned position.
 5. Theelectromagnetic actuator of claim 4, wherein the shell includes acircumferentially extending projection and a rim member that is disposedon a side of the circumferentially extending projection opposite thecavity, and wherein an end of the armature is configured to abut the rimmember when the armature is in the extended position.
 6. Theelectromagnetic actuator of claim 5, wherein the circumferentiallyextending projection includes a first tapered face on a side oppositethe cavity, wherein the armature includes a second tapered face that isconfigured to be attracted to the first tapered face when the coil isenergized, and wherein the first and second tapered faces are spacedapart from one another when the armature is in the extended position. 7.The electromagnetic actuator of claim 5, further comprising a sensorthat is coupled to the frame, the sensor being configured to sense aposition of the plunger or the armature in at least one position and togenerate a sensor signal responsive thereto.
 8. The electromagneticactuator of claim 7, wherein the sensor is configured to sense the rim.9. The electromagnetic actuator of claim 1, wherein the shell isdisposed about the axial ends of the coil and wherein a portion of theshell guides the armature as it translates between an extended positionand a retracted position.
 10. The electromagnetic actuator of claim 9,wherein the portion of the shell that guides the armature has an outsidediameter that is smaller than a diameter of the portion of the shell towhich the armature is attracted when the coil is energized.
 11. Theelectromagnetic actuator of claim 1, wherein the shell is formed of twodiscrete shell members that are disposed about opposite axial ends ofthe coil.
 12. The electromagnetic actuator of claim 1, wherein the shellcomprises a continuous annular surface for attracting the armature. 13.An electromagnetic actuator comprising: a coil assembly having a coil,which is energizable to generate a magnetic field, and a shell that isformed of a ferrous material, the shell defining a cavity into which thecoil is received, the shell having a circumferentially extendingprojection that encircles an axially extending portion of the coil, theshell further having a first cylindrical guide surface; and an armaturethat is formed of a ferrous material and which is movable relative tothe coil assembly along a translation axis due to a magnetic fieldproduced by the coil when the coil is energized, the armature having asecond cylindrical guide surface that is slidably engaged upon the firstcylindrical guide surface; wherein magnetic field lines associated withthe magnetic field generated by the coil extend through an interfacebetween the first and second cylindrical guide surfaces and where themagnetic field lines further extend through an interface between acircumferentially extending surface on the armature and acircumferentially extending surface on the circumferentially extendingprojection.
 14. The electromagnetic actuator of claim 13, wherein atleast one of the circumferentially extending surfaces isfrusto-conically shaped.
 15. The electromagnetic actuator of claim 13,wherein the shell comprises a rim member that is disposed on a side ofthe circumferentially extending projection opposite the cavity, andwherein an end of the armature is configured to abut the rim member whenthe armature abutted against the shell.
 16. The electromagnetic actuatorof claim 13, further comprising a plunger coupled to the armature formovement therewith.
 17. The electromagnetic actuator of claim 16,wherein the armature includes a circumferentially extending rim memberagainst which the plunger is abutted.
 18. The electromagnetic actuatorof claim 13, further comprising a frame that is defined by a generallyU-shaped circumferentially extending channel, the coil assembly and thearmature being received in the frame.
 19. The electromagnetic actuatorof claim 18, further comprising a sensor coupled to the frame, thesensor being configured to sense a position of the armature and generatea sensor signal responsive to the positioning of the armature in atleast one predetermined position.